The invention relates to a method of manufacturing a planar optical component, in which at least one groove is etched in a glass substrate, use being made of a metallic mask which is applied to the substrate, after which the substrate is covered with a layer of glass having a refractive index which is higher than that of the substrate, the groove being filled entirely, after which excess glass is removed.
A similar method is described in the published Japanese Patent Application JP 56-135808, in which quartz glass is used as a substrate and a titanium layer having a thickness of 1 .mu.m is used as a mask. After grooves have been etched with a depth of 10 .mu.m, the titanium layer is removed by means of plasma etching. Subsequently, a layer of glass having a high refractive index is applied by means of chemical deposition from the vapour phase, after which a heating step is carried out to fuse the glass particles into a glass layer having a thickness of 30 .mu.m, which glass layer contains recesses of approximately 2 .mu.m at the surface over the grooves. Then, the excess glass is removed from the entire surface, at least up to the original surface of the substrate, by means of plasma etching. Finally, a protective layer of glass is applied having a refractive index which is equal to that of the substrate, for example, by means of chemical deposition from the vapour phase.
The known method enables patterns to be manufactured with a high lateral accuracy, for example with lines having a width from 1 to 5 .mu.m, but a high accuracy as regards depth cannnot be attained.